In the last column we looked at using thin belts on the WASP. Knife sharpening deserves a bit more attention because it is a common task and the WASP does it so well.

A belt sander is far more preferable than a bench grinder for knives. A bench grinder is too agressive for knives. The WASP has the added advantage of speed control already built into your drill, so you can avoid the danger of overheating and damaging the heat treatment of your blade. Its a better working position too.
A belt width of 25mm to 50mm is suitable for grinding kitchen knives and woodcarving knives. Refer to the previous article to see how you can make your own belts.

Bevel Angles and Edge Condition
Kitchen Knife:- a slightly serrated edge is probably better for cutting vegetables, especially tomatoes, so using the belt alone will finish the job. The same applies for meats and bread. Finishing with a belt grade of about 400# will be about right for this. Using an included angle of say 10° will be suitable.

Kitchen knives used for chopping, especially if bones are present, would be better with an included angle of say 30°. An angle of 50° for a cleaver will avoid edge nicking.

Wood Knife:- a highly polished edge (like a chisel or plane iron) is appropriate here, with an included angle of say 10° for soft wood; more for harder timbers; experience and personal preference will determine this. If your knife is in a poor state start with a belt grit of about 180#, then progress through to about 400#. After this you are ready for a much finer belt - say 800# silicon carbide, or alternately, I have a personal preference for a stropping/polishing action using a leather belt on the WASP, charged with a honing compound. Note:- a barrel shaped drum is required when using leather belts (see Tips No. 8 for barrel shaped drum).

A honing compound specially formulated for carbon steel & high speed steel, containing chromium oxide, is best here. Charge the leather belt fully from edge to edge and then continue to polish the edge of the knife.

When sharpening a knife for wood a highly polished edge with minimal micro-scratches is just as important as the included angle you have chosen. We have all cut ourselves on broken glass and know how sharp that is - yet it probably had an included angle of 90°- but consider how highly polished that edge is - that is the secret to a perfect cutting edge. A very small included angle can facilitate entry into the work but can weaken the edge too so a compromise is sought through experimentation.

If you have difficulty finding some of the belts (including the leather belt) mentioned in this column go to our on-line shop.